I gather that nickel would be the only metal to come in contact with the liquid.

Maybe it would help if the description for products could describe what metal would be coming into contact with the liquid.

One more thing that confusers me is the statement: Do not use silver with nickel in the same system. What if it had copper plated silver for some strange reason. Would it still be bad? I understand they are probably talking about the use silver kill coils. Or maybe my definition of system is a little off. Maybe only metals that come into contact with the liquid are considered part of the system, but the thing is, I don't know. It is unclear to me, so I am asking. Please help. Thank you for your time.